Light sensitive diazo-type layers and method of use and production



Patented Sept. 24, 1940 UNITED STATES LIGHT SENSITIVE DIAZO-TYPE LAYERS AND METHOD OF USE Werner Paul Leuch, Lon

Eugene Dietzgen 00., tion of Delaware No Drawing. Anl licati AND IRODUCTION don, England, assignor to Chicago, 111., a corporaon July 21, 1939, Serial No. 285,663. In Great Britain July 7, 1938 2 Claims.

The present invention relates to the manufacture of light sensitive layers for use in the diazotype photographic process and for. the production of prints in accordance with the diazo-type print- W ing process. V

In accordance with the diazo-type printing process, prints are produced on a preferably white background by the formation of diazo dies in situ along preselected areas or lines corresponding to an original image.

According to one method of carrying out this process, a paper or other suitable support, coated with a light sensitive diazo salt, is exposed to light under a tracing or other image and then developed by means of a solution of an azo coupling component. Formation of an azo dyestufi occurs only at the shaded areas overlaid by the lines of the tracing to produce a corresponding printed image.

According to another method of procedure, the light sensitive layers contain not only the diazo component but also the azo coupling component, so that development after exposure of the print may be effected merely by means of an alkaline vapor such as ammonia vapor.

While coupling normally proceeds only under alkaline conditions, I have disclosed in my United States Patent No. 2,1139% an invention enabling development under neutral or acid conditions. My foregoing invention is of great practical signiiicance as obviating undesired discoloration and instability of the prints resulting from the use of alkaline developers, particularly in the presence of phenolic coupling components.

Irrespective of theprocedure employed in carrying out diazo-type processes, dyestuff components must be carefully selected if a satisfactory print is to be produced. By way of example, the diazo salt must be light sensitive and capable of rapidly decomposing under the influence of light rays of predetermined intensity. It will be obvious that to produce a print having a white background, the decomposition product of the salt must be white or colorless. At the same time, the light sensitive product must possess a good stability and permanence during periods of storage prior to exposure, and similarly be capable of rapidly coupling with conventional and preferred coupling components. The final color must not only be fast and permanent but free from spreading or bleeding, so that the printed lines form sharp, accurate reproductions. In order to permit the original coating of the paper or the support with the light sensitive layer the diazo salt need necessarily possess a substantial degree of til solubility, a property lacking in many of these compounds.

- or even greater importance is the color of the final print. Great practical difliculty has been experienced in securing prints having the desirable black lines on a white background, and particularly black lines tending to blue-black, green-black, or grey-black, as compared with the undesirable maroon, brown, or orange colors.

It will be evident from the foregoing, as well as other limitations which will occur to those skilled in the art, that a difl'lcult and serious problem attends the development of suitable dye stuff components and particularly diazo-components for use in the case of development under acid conditions, in accordance with my foregoing patent, since these components must also be capable of coupling under acid conditions.

It is known, as stated in United States Patent No. 1,816,989, that certain diazo salts are well suited for the diazo-type process, which contain, besides the diazotizable amino group also an acyl amino group, compounds derived from l-amino- 2:5-diall oxy-l-benzoylamino benzene, being represented as being particularly important. Certain compounds coming within the purview of the disclosure of ,Patent No. 1,816,989 are especially suitable for development under neutral or acid conditions, that is, by means of developers free from alkaline materials. The notable disadvantages exhibited by these compounds, however, are their undesirably low sensitiveness to light; the tendency to bleed on development, causing lines to become blurred, particularly at a low pH such as about 5.2; and the fact that the background of the prints does not satisfactorily bleach out during light exposure, thus tending to result in a discolored background. Of even greater importance is the fact that the resultant prints, particularly when employing conventional coupling components such as phlor-glucine, are of brown or brownish-lrlack color, tending to become reddish where copies from pencil drawings are made.

British Patents No. 449,341, accepted June 25, 1936, and 454,665, accepted October 6, 1936, disclose light sensitive diazo-type layers distinguished from the foregoing in that they contain diflerent acyl groups. Thus the former patent employs, in place of the acyl group a thioglycol acid residue, while the second British patent substitutes a phenoxy-acetyl residue. Although these compounds are an improvement upon the benzoylamino derivatives in respect to their faster printing properties, they are in each instance zoylamino derivative.

less soluble or less stable and result in prints of brownish or violet-brownish shades of black.

In accordance with the present invention, there is provided a light sensitive layer having great sensitiveness to light and producing prints having very sharp lines without the slightest trace of bleeding. The present invention provides prints which are neutral grey-black or greenblack shades on an excellent white background. The present prints have an excellent stability and permanence and are formed from diazo salts which are subject to rapid and easy development.

According to the present invention, it has been found that such remarkably clear light-sensitive layers can be obtained if the aforementioned benzoylamino radicle is replaced by a phenylacetyl radicle. The new compounds have the following formula:

O-alkyl and produce neutral grey-black to greenish-black shades on a background much whiter than that which can be obtained using the foregoing ben- The resulting prints have perfectly sharp lines, and half-tones from images such as pencil drawings exhibit neutral grey shades. In particular, l-aminol-phenyl-acetylamino-2:5-diethoxy-benzene has been found to give excellent results, but other alkoxy groups such as methoxy, propoxy, and butoxy may be substituted for the ethoxy' groups of the fore going compound and equivalent results obtained.

One method of making the new compounds is as follows: l-amino-Z:5-diethoxybenzene is acylated by suspending the finely powdered base in water, adding the calculated quantity of sodium carbonate and phenyl-ac'etyl chloride. The amount of carbonate used should be such that at the end of the reaction the liquid remains faintly alkaline.

The mixture is then heated on the water-bath to a temperature of 50-60 C. After about thirty minutes it is cooled and filtered. After purification the acyl-amino is then dissolved in glacial acetic acid and mono-nitrated. The nitrocompound is then isolated and reduced in alcoholic solution with iron and hydrochloric acid, or iron and acetic acid.

After the reduction is completed, the liquid is rendered alkaline with sodium carbonate to precipitate the iron salts present, and filtered. The base can then be isolated in the form of its hydrochloride by the addition of water and hydrochloric acid. After purifying the base, it can be diazotized in the usual manner and obtained finally as a dry diazo double salt by precipitation with zinc chloride, or any other suitable metal salt.

The foregoing illustrates only one method of producing the present compounds, in order to enable one skilled in the art to practice the present invention. It will be understood that there are a number of other processes by which the same'compounds may be synthesized, and the present invention contemplates the use of these compounds regardless of their manner of synthesis.

The following illustrated examples exemplify the practice of the present invention:

Example 1 40 grams of the zinc chloride double salt of 4-diazo-l-phenylacetylamino 2:5 diethoxybenzene. 15 grams of tartaric acid and 10 grams of aluminium sulphate are dissolved in one litre of water. The paper is coated with this sensitive solution and dried: after exposure to light under a drawing it is developed with a developer containing:

' Phloroglucinol grams..- 2 Sodium benzoate do 15 Sodium formate -1 do 80 Tartaric acid do 2 Saponin do 0.2 Water or 568 Prints with a clean white background and sharp black lines are obtained. The printing speed of this paper is approximately 25% greater than that of a paper which is made using equimolecular quantities of the corresponding benzoylamino derivative.

Example 2 37 grams of the zinc chloride double salt of 'd-diazo-1-phenylacetylamino-2: 5-di-n-propoxybenzene, 15 grams of tartaric acid and 10 grams oi aluminium sulphate are dissolved in one litre of water.

Paper sensitized with this solution and printed under a drawing will, when developed with the developer given in Example 1, produce deep black lines on a white ground. The color of the lines is greyer in shade than those obtained with the ethoxy derivative.

Example 3 Example 4 37 grams of the zinc chloride double salt of 4-diazo-l-phenylacetylamino-Z:5 di-(di-B-ethoxyethoxy) -benzene 25 grams of tartaric acid and 13 grams of aluminium sulphate are dissolved in one litre of water.

. Prints obtained from paper coated with the above solution and developed with the developer given in Example 1 give green-black lines.

From the foregoing it will be apparent that the present invention provides sensitized layers capable of being treated by known methods to produce final prints of the desired character, the process being free from disadvantages which either in whole or in part have characterized the present art. Itis to be understood that while the above examples illustrate certain methods of carrying out the present invention, the present sensitized layers may be transformed into prints in accordance with other conventional methods known in the art.

Attention is further directed to the fact that while the foregoing phenyl-acetyl amines constitute the preferred embodiment of the present invention. certain, although not all advantages of the present invention are obtained in the case of aryl-alkacyl amines broadly. Such is the case where instead of the phenyl group a naphthyl pect of the present invention. On the other hand, as longer chain alkacyl groups are substituted for the foregoing acetyl group of the phenyl-acetyl residue, a further increase in printing speed has been observed. As the lengthening of the alkacyl chain increases, however, the coupling speed as well as-the solubility of the resultant compound diminishes. Such compounds, therefore, while coming within the broadest aspect of the present invention, are to be distinguished from the specific, preferred substances forming the preferred embodiment.

The invention is hereby claimed as follows:

1. An article of manufacture for use in the production of diazo-type prints comprising a base having thereon a light-sensitive layer comprising a diazo compound of an amine having the following structural formula:

2. An article of manufacture for use in the production of diazo-type prints comprising a base having thereon a light-sensitive layer comprising a dlazo compound of an amine having the fol-- lowing structural formula:

WERNER PAUL LEUCE. 

